a) Field of the Invention
The present invention relates to a semiconductor device and its manufacturing method, and more particularly to a semiconductor device and its manufacturing method, using selective growth.
b) Description of the Related Art
High speed operation and high integration of semiconductor devices are strongly requested. To meet such requests, miniaturization as well as high integration of semiconductor elements is necessary. If the degree of miniaturization is less than integration, the area of a chip increases, posing a problem of a delay of signal transmission time and the like. For the miniaturization of semiconductor elements, fine processes such as reactive ion etching (RIE) are used.
The surface of semiconductor subjected to the fine process such as RIE, however, may have damages. The damaged semiconductor surface deteriorates the characteristics of semiconductor crystal and lowers the performance of a semiconductor device.
If many fine processes are executed to miniaturize semiconductor elements, there is a limit of miniaturization from the consideration of the performance of semiconductor elements.
It is effective for the miniaturization of semiconductor devices to simplify the structure of electronic functional elements capable of performing predetermined circuit functions. For example, if the structure of a static random access memory (SRAM) generally made of six transistors can be simplified, the semiconductor device providing predetermined circuit functions can be made compact.
As such functional elements having simplified structures and providing predetermined circuit functions, there are known double-emitter hot electron transistors (DEHET), double-emitter hetero bipolar transistors (DEHET), and the like.
In the case of a double-emitter resonance hot electron transistor (DERHET), electron levels in the resonance tunnel diode structures are quantized and the transistor shows the negative differential resistance characteristic.
In DERHET, two voltage values are stable relative to a same current value. Therefore, two stable states are generated when predetermined voltages are applied to double-emitters. An SRAM cell can be made by using this function.
As described above, use of a fine process such as RIE results in damages on the surface of semiconductor and limits the performance of a semiconductor device. It has been long desired therefore to manufacture a semiconductor device having a miniaturized structure by using a fine process as less as possible.
If semiconductor elements having such a miniaturized structure can provide a predetermined circuit function with a simplified circuit structure, it can greatly contribute to compacting a semiconductor device.